Methods of performing useful work by utilising sources of heat that are external to a working apparatus have been described. However, there are available sources of heat energy that have either not been effectively utilised to perform useful work.
It would be desirable to use relatively low temperature sources of heat energy or to utilise heat energy from sources that is presently being wasted. However, it will be appreciated that the invention is not limited to energy sources of low temperature. Fluid with temperatures of up to 100° C. and beyond could be utilised by the invention. The temperature of the energy source may determine the type of thermal energy converter, such as all whether an evaporator or condensor may be used.
For example, solar radiation can be used to readily heat water to modest temperatures such as 40° C.–60° C. and it would be advantageous if such heat energy could be used to perform useful work. Heated water or heated water vapour can be obtained from hydrothermal sources. For example, bore water extracted from ground aquifers and used for irrigation or for drinking water for stock or for domestic use in remote locations is often at all elevated temperature and it would be beneficial if the heat energy of such water could be reduced and utilised to perform useful work. Also there are many possible sources of heat energy that are presently unutilised or underutilised such as heat energy in exhaust gases or particles such as smoke: (a) from internal combustion engines, such as engines driving generators or even being used in vehicles and (b) discharged from industrial plant and equipment.